Titration is used for determining a concentration of a constituent of a solution or for determining a characteristic of a solution. In some titrations, acidity or alkalinity is determined by adding an acid or base to a solution containing an indicator. When the pH reaches a particular value, the color of the indicator changes. For example, a common indicator is phenolpthalein which is colorless in acidic solutions, but is red in solutions having a pH exceeding nine. Other indicators are available for responding to the presence of particular ions in solution. For example, permanganate ions respond to the presence of iron or nitrite ions in solution. A characteristic of a solution of unknown concentration (the analyte) containing an indicator may be determined from the quantity of a titrant of known concentration added to the solution to bring about a change in indicator color. Alternatively, a reverse or back titration may be performed, where the titrant is a solution of unknown concentration (the analyte), and a solution of known concentration is used as the titrand.
Titrations are conveniently carried out in a laboratory environment with a relatively inexpensive apparatus since conditions can be easily controlled. However, in manufacturing operations where conditions are not so easily controlled, use of titration to test or analyze and thereby control the characteristics of various chemical baths is more difficult and expensive. In some situations, analytical techniques other than titration are employed to monitor characteristics of solutions, including spectroscopy techniques that require an expensive and complex apparatus.
Employment of titration as a process control technique is difficult, as human error is introduced when technicians must judge the change in color of the indicator at the end-point of the titration. Furthermore, continuity in judging the titration end-point is jeopardized when multiple technicians run titrations over time. Accordingly, there is a need for an automated, inexpensive titration apparatus for use in process control that can automatically determine the end-point of a titration reaction in an industrial setting.